I first read the Alvin Maker series when there were only three of them, in the early 90s, and as I recalled, the first three were the only ones I had considered worth rereading. I went back to this because I started working on an epic fantasy based on early Mormonism and this is, as far as I know, the only other one! Alvin Maker follows a lot of Joseph Smith's life arc--he has a leg injury, lives in a world of folk magic and eventually acquires a magical golden object. Unfortunately the series doesn't do much with the Mormon conceit other than playing around with the folk magic of Smith's early years.
30 years on, there's a lot that holds up and a lot that doesn't, and I didn't quite get through Prentice Alvin in the end. Seventh Son has some wonderful rich detail about frontier life in America and it also has page after page after page of Card's gleeful fan-fiction style rewriting of history and musing on what it means to be American. His alternate history is actually pretty great--the American colonies splintered into multiple nations and re-colonized British provinces and thus the new United States includes one slave state, the Iroquois Six Nations as a state, and a whole lot of interesting politics--but the lens never goes quite wide enough for it to feel like "epic" fantasy, even in Red Prophet, the most epic of the books.
Seventh Son mostly focuses on Alvin Maker's life as a Maker, a special Chosen One gifted with a kind of uber-folk-magic, and a struggle between Alvin and the Unmaker-possessed local preacher. Card also reverses the traditional notion of water as a life-giver and has water be the seat of the Unmaker, a funny historical nod to Joseph Smith's vision of "the Destroyer riding with power on the face of the waters."
Red Prophet has a major warning for some very bad takes on Native American characters and story, but given that it's by a right-wing boomer written in the 80s, it was actually better in this regard than I thought it would be, and it's easily the best of the three books. It follows multiple points of view across a magical version of Tecumseh and Tenska-tawa's struggle, their divided viewpoints on pacifism and war, their struggle against Governor Harrison, and finally the massacre of Tenska-tawa's peaceful forces. I hated some things about the book, especially the white savior-ism of Alvin's plotline with Tecumseh and the very bizarre chapter where Tecumseh reveals his "double life" lived as a white man, but the ending had to be one of the better fantasy takes on American colonialism, where all those who massacred Tenska-tawa's people are marked with bloody hands forever, and are forced to tell their stories, but William Henry Harrison parleys his pride in said genocide into a Presidential victory. Nice commentary on how American genocide became "Manifest Destiny."
Prentice Alvin is a little dull after Red Prophet, and I put the book down after a pretty horrific sequence in which a couple of villains discuss the moral rightness of raping slaves. I get that they weren't supposed to be heroic but jeeeeeez (and btw, what is with boomers who spend PAGES and PAGES in the heads of absolutely loathsome characters? Stephen King does it too. Are they getting payoffs from the showerhead industry?).
As someone who loves Mormon history, I can't help but see that Prentice Alvin runs into some problems with the Joseph Smith parallel. The longer Card went into this series, the more he'd have to look at what Joseph Smith and Brigham Young actually did, and how close he'd want to hew to it. Sadly, for all that they believed they would be the saviors of Native Americans, Mormon settlers were just as complicit in Native genocide, and after an initial flurry of abolitionism they firmly fence-sat the Civil War and were one of the most backward racist organizations of the 20th century until 1978. I never read the last two books in the series, but as I recall, Card had some sort of magical barrier appear on the Mississippi that allowed a pan-Indian nation to develop in the West and interact in Alvin's Crystal City.
So it doesn't really do much with Mormonism, overall.
Card is a really controversial writer these days. I don't believe anyone can really keep their politics out of their writing, but especially not a writer obsessed with moral and ethical behavior like Card, and I stopped reading his work when the Shadow series essentially seemed like a polemic for his support of the invasion of Iraq.
Even these books, which come from a period where Card was more politically moderate, are pretty annoying. Card is obsessed with the idea of the virtuous, strong main character who exists mostly to be RIGHT and to explain to others that they are RIGHT and only occasionally be corrected by teachers. It's no wonder that he even wrote a book trying to redeem Christopher Columbus via Columbus's good intentions.
TL;DR: Seventh Son & Red Prophet are worth rereading, but haven't aged all that well.